Magnetic head heating element in a disk drive

ABSTRACT

An object of the present invention is to prevent a spacing between a magnetic head and a writing medium at low temperature from increasing to cause a writing/reading error, and to prevent the magnetic head element protruded by a temperature increase from colliding with small protrusions on a magnetic disk surface, and to prevent damage on the element, and to prevent the occurrence of thermal asperity. In order to attain the object, a magnetic head slider is provided, which includes a magnetic head element supported on a rotating magnetic disk via a gap to write or read information on the magnetic disk, and a heat source for heating the magnetic head element. A magnetic disk device is further provided, which includes a magnetic head slider.

TECHNICAL FIELD

The present invention relates to a floating type or sliding typemagnetic head slider having a magnetic head for reading and writinginformation on a magnetic disk, and a magnetic disk device including themagnetic head slider.

BACKGROUND ART

In order to respond to the need for higher recording density of amagnetic disk device, it has been more necessary to reduce a flyingheight of a magnetic head slider (simply referred to it as a slider) inrecent years. Meanwhile, the smaller a flying height of a slider, R/W(Read/Write) elements are more prone to collide with small protrusions,which are resulted from a rough surface of a magnetic disk. In recentyears, a slider has had a small flying height of 30 nm or less relativeto a magnetic disk, so that the probability of collision has increasedbetween small protrusions on a surface of a magnetic disk and a magnetichead element (simply referred to it as a head element). In the case of amagnetoresistance effect type head, when a head element collides withsmall protrusions, the element generates heat and an abnormal signalappears due to thermal asperity (hereinafter, abbreviated as TA).Further, in general, a protective film made of carbon or the like isprovided on a surface of a head element to prevent damage such ascorrosion. When the protective film on the surface of the head elementwears due to collision with small protrusions on a surface of themagnetic disk, the head element cannot be protected and damage such ascorrosion is more likely to occur, resulting in shorter lifetime of themagnetic disk device.

JP-A-10-269527 specification discloses means for avoiding collisionbetween small protrusions on a magnetic disk and an element so as toprevent an abnormal signal caused by thermal asperity (TA) on amagnetoresistance effect type head. The means can avoid collision bymaking a step such that a magnetic head element structure has a recessedpart relative to a front slider in.

When a magnetic signal is recorded and reproduced, since current isapplied to a magnetic head element, the head element generates heat anda temperature rises. Moreover, due to heat generated on a spindle motoror the like, a temperature rises entirely on a magnetic disk device. Thetemperature may increase to 60° C. On the other hand, in the headelement part, the magnetic head element is generally formed by a nickelalloy and a cobalt alloy, and an insulating film is made of a ceramicsuch as alumina. The nickel alloy and the cobalt alloy are larger inthermal expansion coefficient than the ceramics of the insulating film.When a temperature rises, the element has a larger amount of thermalexpansion than the ceramics of the insulating film. Thus, the elementprotrudes in a thickness direction of the slider, that is, in adirection of a disk surface.

Hereinafter, as one example a protruding amount of the element will becalculated. It is assumed that a material of the element is a Ni—Fealloy and a linear thermal expansion coefficient δl/l is set at1.45×10⁻⁵/K. The element is 0.05 mm in length in a thickness directionof the slider. The insulating film is made of alumina and has a linearthermal expansion coefficient δl/l of 7.5×10⁻⁶/K. Here, when it isassumed that a temperature increase is 20K and the element and aluminaare expanded independently, a protruding amount δl of the element is 7nm (=7.0×10⁻⁶/K×20×0.05×10⁶).

According to the technique disclosed in JP-A10-269527 specification, inthe case of a small step between the head element part and the frontslider part, when a temperature rises largely, due to protrusion of theelement that is caused by thermal expansion, for example, when theslider flies, the element part is disposed at the lowest floating point(the closest point to the disk surface). Hence, the element is morelikely to collide with the small protrusions on the surface of themagnetic disk, resulting in an abnormal signal due to damage on theelement and thermal asperity.

Moreover, in the case of a large step between the head element part andthe front slider part, or in the case of use in the environment at lowtemperature (e.g., around 0° C.), a distance (magnetic spacing) betweenthe head element and a magnetic medium is increased when the sliderflies, resulting in inability to perform recording and reading.

An object of the present invention is in a magnetic head slider and amagnetic disk device using the same, to provide a magnetic disk deviceor a magnetic head slider which can prevent collision between a headelement and small protrusions on a surface of a magnetic disk and canreduce damage and thermal asperity on the head element even when atemperature rises. Further, another object is to provide a magnetic diskdevice which can perform normal recording and reproducing in response tochanges in ambient temperature such as a temperature in a magnetic diskdevice and an outside air temperature.

DISCLOSURE OF THE INVENTION

The above described object is attained by providing a magnetic headslider which has a magnetic head for writing or reading information on amagnetic disk and has a heat source around the magnetic head part oraround elements in addition to writing/reading elements.

Namely, the above described object is attained by providing magnetichead elements which is supported on a rotating magnetic disk via a gapand records or reproduces information on the magnetic disk, and amagnetic head slider having a heat source for heating the magnetic headelements. Or the object is attained by providing a film for heatingmagnetic head elements for writing or reading information on a magneticdisk, and a magnetic head slider having a heat source for heating thefilm.

Further, the above described object is attained by providing a magnetichead slider which has magnetic head elements for writing or readinginformation on the magnetic disk and regulates deformation occurring dueto changes in temperature of the magnetic head elements. Or the objectis attained by providing magnetic head slider which has a film heatingmagnetic head elements for writing or reading information on themagnetic disk and regulates deformation occurring due to changes intemperature of the film.

Also, the above described object is attained by a magnetic disk devicewhich has a rotating magnetic disk, a slider supported on the magneticdisk via a gap, a suspension for supporting the slider on the magneticdisk via a gap, and a carriage for movably supporting the supportingmeans on the magnetic disk. The slider comprises magnetic head elementsfor writing or reading information on the magnetic disk and a heatsource for heating the magnetic head elements. The magnetic disk devicecomprises means for regulating heat generation of the heat source.

Further, the above described object is attained by providing a magneticdisk device which has a rotating magnetic disk, a slider supported onthe magnetic disk via a gap, a suspension for supporting the slider onthe magnetic disk via a gap, and a carriage for movably supporting thesupporting means on the magnetic disk. The slider comprises a filmheating magnetic head elements for writing or reading information on themagnetic disk, and a heat source for heating the film. The magnetic diskdevice comprises means for regulating heat generation of the heatsource.

Further, the above described object is also attained by a magnetic headslider (magnetic head) which includes (a magnetic head for writing orreading information on a magnetic disk, the magnetic head having atleast) a thermal expansion material disposed on the disk side from acentral surface in a thickness direction of the slider.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an enlarged view showing a magnetic head part of Embodiment 1in a magnetic head slider of the present invention;

FIG. 2 is a side view showing the magnetic head slider of FIG. 1;

FIG. 3 is a diagram showing an example of an electric conducting film ofthe magnetic head slider shown in FIG. 1;

FIG. 4 is a diagram showing the electric conducting film bonded to therear of the head in a traveling direction of the slider;

FIG. 5 is a diagram taken from the rear of the head in a travelingdirection of the slider;

FIG. 6 shows an example of displacement measurements of a head elementrelative to changes in ambient temperature when the electric conductingfilm is not formed;

FIG. 7 shows an example of displacement measurements of the head elementwhen power is supplied to a light coil when the electric conducting filmis not formed;

FIG. 8 is a diagram showing changes in temperature of the head elementswith time when direct current of 40 mA is applied to the light coil;

FIG. 9 is a diagram showing a state in which magnetic head elementsprotruded by heat collides with a small protrusion on a surface of amagnetic disk;

FIG. 10 is a side view showing a magnetic head part having a temperaturesensor bonded to the rear of the head;

FIG. 11 is a side view showing a magnetic head part having a temperaturesensor bonded to the back of the head;

FIG. 12 is a diagram taken from the back of a magnetic head part havingtemperature sensors bonded to the side of the head;

FIG. 13 is a side view showing a magnetic head part having electricconducting films connected to a load/unload control circuit;

FIG. 14 is a flowchart diagram showing loading/unloading control of theslider;

FIG. 15 is an enlarged view showing a magnetic head part of anotherembodiment in the magnetic head slider of the present invention;

FIG. 16 is a side view showing the magnetic head slider of FIG. 15;

FIG. 17 is a conceptual illustration showing the head element protrudingto a magnetic disk 1 due to thermal expansion;

FIG. 18 is an explanatory drawing showing the effect of a thermalexpansion film in the magnetic head slider of FIG. 15;

FIG. 19 is an enlarged view showing a magnetic head part of anotherembodiment in the magnetic head slider according to the presentinvention;

FIG. 20 is an explanatory drawing showing the effect of a thermalexpansion film of FIG. 19 of the present invention;

FIG. 21 is an enlarged view showing a magnetic head part of anotherembodiment in the magnetic head slider according to the presentinvention; and

FIG. 22 is a perspective view schematically showing the configuration ofa magnetic disk device according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The following will discuss embodiments of the present inventionreferring to the drawings. Referring to FIGS. 1 to 4, Embodiment 1 of amagnetic head slider according to the present invention will bediscussed by taking a magnetoresistance type head as an example. FIG. 1is an enlarged side view showing a magnetic head, and FIG. 2 is a sideview showing the magnetic head slider.

Further, FIG. 22 schematically shows the configuration of a magneticdisk device according to the present invention. FIG. 22 is a perspectiveview showing a magnetic head device 100 having a magnetic head slider104, which will be discussed below.

In a magnetic disk device 101, a hub 103 is driven and rotated around arotary axis 102 by a spindle motor (not shown). A plurality of rotatingmagnetic disks 101 is attached to the hub 103 inside a casing (case)111. The slider 104 positioned on a surface of the disk floats via asmall gap due to the rotation of the magnetic disk 101 and is supportedby a suspension 105.

At a tip end side of the suspension 105, a gimbal (flexure) part isprovided such that the slider 104 can rotate longitudinally andlaterally around the axis. The gimbal part is attached to the suspension105 so as to support the slider 104.

The suspension 105 is attached to a carriage 106 at a basal side whichis opposite from the slider 104, so that the suspension 105 is supportedon the magnetic disk. The carriage 106 is attached so as to freelyrotate around a pivot axis 108 of a pivot part 107, which is on theopposite side of the suspension. The suspension 105 and the slider 104are positioned on the magnetic disk 101 due to electromagnetic forceapplied to a coil by a voice coil motor 110. The voice coil motor 110includes a coil which is attached and supported on a coil bobbin 109provided on the other side of the carriage 106 with the pivot 107 beingdisposed therebetween.

Information on the disk is written or read by the magnetic head moundedon the magnetic head slider 104, which is positioned on the magneticdisk 101, and a signal of the written/read information is transmitted tothe outside of the magnetic head or the magnetic disk device through asignal line provided on a flexible print circuit (FPC).

The configuration of the present embodiment will be discussed below. Amagnetic head 2 is mounted on an air flow-out end of a slider 1. A headelement 3 is constituted by shield films 4 a and 4 b, amagnetoresistance type reading element 5, an insulating film 6, a coil7, a magnetic core 8, or the like. Further, two electric conductingfilms 9 a and 9 b, which generate heat due to application of voltagethrough wiring 11 a, 11 b, 11 c, and 11 d, are formed substantially inparallel near the magnetic head part 2 or the element part 3 at apredetermined interval so as to sandwich the head element part 3. As acontrolling method, when an ambient temperature is low or when theelement has a low temperature, voltage or current is applied to theelectric conducting films and heat is generated on the electricconducting films to maintain a fixed and proper temperature of theelement. Moreover, when an ambient temperature is high or when atemperature of the element is increased by writing and reading, it isfeatured that voltage or current applied to the electric conductingfilms is reduced to maintain a proper temperature of the element.

Here, a surface of the slider 1 that opposes the disk is different inheight from a surface of the head element 3 that opposes a disk. Thedifference is referred to as machining step (PTR) 10. The machining stepoccurs when a floating surface is polished. Since the head element 3 islower in hardness than the slider 1, polishing is made more frequentlythereon and grows more concave than the surface of the slider 1.

In the present embodiment, it is not always necessary to provide twoelectric conducting films, so that a single film may be also applicable.Besides, two or more electric conducting films may be provided formaking a temperature uniform on the element part.

Also, regarding a material of the electric conducting films, a materialsuch as metal and semiconductor is applicable as long as heat can begenerated by applying voltage. For example, a nickel alloy and a cobaltalloy can be selected. Further, electrical resistance of the electricconducting films can be selected as necessary. For example, a resistancecan be set at 10 Ω.

Besides, the size of the electric conducting films 9 a and 9 b is setsuch that the films can be disposed in the magnetic head 2. For example,a thickness is 10 to 50 μm, a width is larger than that of the element,and a length in a thickness direction of the slider is equal to that ofthe element. In addition, although the present embodiment employs theelectric conducting films, lumps or lines made of an electric conductivematerial are also applicable. In short, any type of material can be usedas long as heat is generated to allow the element to increase intemperature due to an applied voltage. For example, as shown in FIG. 3,a slim and continuous structure may be adopted. Moreover, it isdesirable that the electric conducting films are configured withoutcausing a magnetic field not interfering with writing and reading whenvoltage is applied.

Besides, in the present embodiment, the electric conducting films 9 aand 9 b are disposed at the front and the rear of the head element alongthe length of the slider. However, the electric conducting films 9 a and9 b may be disposed on the right and left in a width direction of theslider. In short, any configuration is applicable as long as heat can besupplied sufficiently to increase a temperature of the element to apredetermined temperature due to applied voltage.

In FIG. 1 of the present embodiment, the electric conducting films areembedded into the magnetic head. However, as shown in FIG. 4, anelectric conducting film 9 e may be bonded to the rear end part of thehead 2. Additionally, as shown in FIG. 5, electric conducting films 9 fand 9 g may be bonded to both sides of the head 2 that correspond toboth of end faces of the slider 1 in a width direction.

Next, referring to FIGS. 6 to 9, the effect of the present embodimentwill be discussed below.

FIG. 6 shows an example of measurement results of deformation amounts onthe head element 3 (in a thickness direction of the slider) relative toa disk surface. The measurement was made while an ambient temperature ischanged on a conventional magnetic head slider where no electricconducting film is formed. Displacement amounts shown in FIG. 6 werestandardized relative to an ambient temperature of 5° C. As shown inFIG. 6, it is found that when an ambient temperature is changed from 8to 60° C., a displacement amount of the head element (protrusion volumein the disk surface direction) reaches 5 nm or more.

FIG. 7 shows an example of measurement results of deformation amounts onthe head element 3 protruding in the disk surface direction. Themeasurement was made while a temperature of the head element is changedby applying power to a coil of a write head in the conventional magnetichead slider where no electric conducting film is formed. As shown inFIG. 7, it is understood that when a temperature of the magnetic headelement is changed in the range from 25 to 125° C., a deformation amountof the head element reaches 13 nm or more.

FIG. 8 shows changes with time in temperature of the head element whendirect current of 40 mA is applied to the write coil. About 1 sec isnecessary from application of current to when the head element increasesin temperature to a fixed value.

As shown in FIGS. 6 and 7, in the case of the conventional magnetic headwhere the electric conducting films 9 a and 9 b are not formed, when atemperature is low (e.g., just after the start of recording), since themagnetic head element is made concave, spacing is increased between themagnetic head element and the writing medium, so that inability to writemay arise. For example, as shown in FIG. 8, assuming that inability towrite continues for 1 sec until the head element increases intemperature, a writing speed normally ranges from several MHz (10⁶) toseveral hundreds MHz. Thus, 1 sec-inability to record and reproduce isequivalent to loss of several mega pieces or several hundreds megapieces of data.

Further, when the head element part 3 has a high temperature due to anincrease in ambient temperature or heat generated on the element itself,the head element approaches to the disk surface as shown in FIG. 9. Whena machining step (PTR) is small, since protrusion is made toward themagnetic disk 12, the protruded head element collides with a smallprotrusion 13 on a surface of the magnetic disk, the head element may bedamaged, or an abnormal signal may occur due to the formation of thermalasperity. Namely, within a range of an ambient temperature of the headelement, a fixed magnetic spacing may not be maintained, awriting/reading error may occur at low temperature, and damage andthermal asperity may occur on the element at high temperature.

In Embodiment 1, the magnetic head 2 is mounted on the air flow-out endof the slider 1. The head element part 3 is constituted by shield films4 a and 4 b, a magnetoresistance type reading element 5, the insulatingfilm 6, the coil 7, a magnetic core 8, or the like. Further, twoelectric conducting films 9 a and 9 b, which generate heat due toapplication of voltage through the wiring 11 a, 11 b, 11 c, and 11 d,are formed substantially in parallel near the magnetic head part 2 ornear the element part 3 at a predetermined interval so as to sandwichthe head element part 3. As a method of controlling a heating volume ofthe electric conducting films 9 a and 9 b, when the element has a lowtemperature, voltage or current is applied to the electric conductingfilms and heat is generated on the electric conducting films to maintaina fixed and proper temperature of the element. Thus, a proper and fixedspacing can be maintained between the element and the writing medium,thereby preventing a writing/reading error at low temperature. Moreover,when an ambient temperature is high or when a temperature of the elementis increased by writing and reading, voltage or current applied to theelectric conducting films is reduced to maintain a fixed and propertemperature of the element. Hence, it is possible to maintain a properand fixed spacing between the element and the writing medium, so thatthe head element does not collide with the small protrusion on thesurface of the magnetic disk. Thus, it is possible to prevent damage onthe head element and an abnormal signal resulted from the formation ofthermal asperity.

Referring to FIGS. 10 to 12, a magnetic head slider according toEmbodiment 2 of the present invention will be discussed. FIG. 10 is aside view showing a magnetic head part having a temperature sensorbonded to the rear of the head. FIG. 11 is a side view showing themagnetic head part having a temperature sensor bonded to the back of thehead. FIG. 12 is a drawing taken from the back of the magnetic head parthaving temperature sensors bonded to the side of the head.

The configuration of the present embodiment will be discussed. Accordingto the present embodiment, in the configuration of Embodiment 1 of thepresent invention, a temperature sensor 14 a is further provided on therear of the magnetic head and a control circuit 15 is provided whichuses the temperature sensor to control voltage or current applied to theelectric conducting films so as to control a temperature of the headelement part 3.

Besides, in the present embodiment, as shown in FIG. 11, a temperaturesensor 14 b may be provided on the back of the magnetic head, or asshown in FIG. 12, temperature sensors 14 b and 14 c may be provided onthe sides of the magnetic head. Moreover, as to a position for providingthe temperature sensor, the neighborhood of the head 2 or the element 3is desirable. However, the temperature sensor may be provided on theslider 1. Additionally, regarding a method of attaching the sensor, thesensor may be bonded, a thin film may be evaporated, or the sensor maybe embedded into the head.

Next, the operation of the present embodiment will be discussed below.In the case of the present embodiment, the temperature sensor 14 a andthe temperature control circuit 15 are provided in addition toEmbodiment 1. Hence, it is possible to control voltage or currentapplied to the electric conducting films 9 a and 9 b by feedback controland to control a temperature of the head element while a temperature ofthe head element 3 is always monitored, and it is possible to prevent awriting/reading error, which is caused by a large magnetic spacingbetween the element and the writing medium at low temperature, anddamage on the element and thermal asperity that are caused by a smallmagnetic spacing between the element and the writing medium at hightemperature. To be specific, when the magnetic head element has a lowtemperature, a voltage (current) is applied to the electric conductingfilms 9 a and 9 b, and the application of the voltage (current) isstopped when the magnetic head element has a high temperature. Asdescribed above, in the present embodiment, feedback on temperature canbe provided by the temperature sensor. Hence, as compared withEmbodiment 1, there is an advantage that it is possible to moreaccurately control a position of the element.

Referring to FIGS. 13 and 14, a magnetic head slider according toEmbodiment 3 of the present invention will he discussed. FIG. 13 is aside view showing the magnetic head part having electric conductingfilms connected to a load/unload (L/UL) control circuit. FIG. 14 is aflowchart showing load/unload control.

The configuration of the present embodiment will be discussed below. Thepresent embodiment is identical to Embodiment 1 of the present inventionin configuration of a head. The head is configured such that the headelement 3 has a machining step (PTR) when current is not applied to thehead element 3 or the electric conducting films 9 a and 9 b. Further,the present embodiment has the load/unload mechanism, and application ofvoltage or current to the electric conducting films is controlled by anoperation command of load/unload control of the magnetic head slider 1.To be specific, a control circuit 16 is provided which reduces voltageor current applied to the electric conducting films 9 a and 9 b or stopsthe application when the magnetic head slider 1 is loaded or unloaded.

The operation of the present embodiment will be discussed below. Thepresent embodiment is characterized in that a load/unload (L/UL) circuitis provided in addition to Embodiment 1 and heat generated on theelectric conducting films is controlled in response to the circuit.(Since the temperature sensor 14 a and the temperature control circuit15 are provided, a voltage or a current applied to the electricconducting films 9 a and 9 b can be controlled by feedback control and atemperature of the head element can be controlled while a temperature ofthe head element 3 is always monitored, so that it is possible toprevent a writing/reading error caused by a large magnetic spacing atlow temperature between the element and a writing medium and damage onthe element and thermal asperity that are caused by a small magneticspacing at high temperature between the element and the writing medium.)

Further, a control circuit 16 is provided, which controls application ofvoltage or current to the electric conducting films by an operationcommand of load/unload control of the magnetic head slider 1 and reducesvoltage or current supplied to the electric conducting films 9 a and 9 bor stops the application when the magnetic head slider 1 is loaded orunloaded. Hence, when the slider is loaded or unloaded, the head elementhas small thermal expansion and a machining step (PTR) can bemaintained. Thus, the head element is not brought into contact with adisk surface upon loading/unloading, thereby preventing damage on theelement. As an example, FIG. 14 shows a flowchart of load/unload controlof the slider. As shown in FIG. 14, when loading/unloading of the slideris controlled, the head element and the disk are not in contact witheach other upon loading and unloading, thereby preventing damage on thehead element.

It is desirable that an initial machining step (PTR) may be set suchthat the head element 3 does not protrude at the highest ambienttemperature. Although the highest ambient temperature of the headelement part is varied depending upon the working environment of amagnetic disk device, heat generated by a spindle motor, thespecification of the head element itself or the like, the highestambient temperature generally ranges from 40 to 80° C. Thus, as shown inFIG. 6 or 7, it is desirable to set an initial PTR at 2 to 7 nm on thebasis of room temperature (25° C.)

Referring to FIGS. 15 and 16, a magnetic head slider according toEmbodiment 4 of the present invention will be discussed. FIG. 15 is anenlarged side view showing a magnetic head part, and FIG. 16 is a sideview showing the magnetic head slider.

The configuration of the present embodiment will be discussed below. Amagnetic head 2 is mounted on an air flow-out end of a slider 1. A headelement part 3 is constituted by shield films 4 a and 4 b, amagnetoresistance type reading element 5, an insulating film 6, a coil7, a magnetic core 8, or the like. Further, two thermal expansion films17 a and 17 b are formed substantially in parallel in a thicknessdirection of the magnetic head 2 or the slider 1 at a predeterminedinterval so as to sandwich the head element part 3. The thermalexpansion films 17 a and 17 b preferably have at least main partsdisposed below a central surface of a thickness of the magnetic head 2or the slider 1, that is, at the side of the magnetic disk.

Regarding a material of the thermal expansion films, for example, in thecase of a nickel alloy, in which an element material has a linearexpansion coefficient δl/l of 1.45×10⁻⁵/K, it is possible to select anickel alloy (δl/l is about 1.45×10⁻⁵/K) and a cobalt alloy (δl/l isabout 1.4×10⁻⁵/K) that are equal to the element in linear expansioncoefficient. Further, as an example of the size of the thermal expansionfilms 17 a and 17 b, it is preferable that a thickness is set at 10 to50 μm, a width is larger than that of the element, and a length in theslider thickness direction is equal to that of the element. In addition,although the films are provided in the present embodiment, lumps made ofa thermal expansion material are also applicable. In short, any type ofmaterial can be used as long as the magnetic head 2 can be deformed bythermal expansion in the disk surface direction.

Next, referring to FIGS. 17 and 18, the effect of the present embodimentwill be discussed. As shown in FIG. 17, in the case of the magnetic headwhere the thermal expansion films 17 a and 17 b are not formed, becauseof heat generated on the element or a temperature increase of the headelement itself, the head element protrudes toward the magnetic disk 10due to thermal expansion. The protruded head element collides with asmall protrusion 11 on the surface of the magnetic disk, so that thehead element is damaged or an abnormal signal appears due to theformation of thermal asperity.

As shown in FIG. 18, the thermal expansion films 17 a and 17 b areformed in the present embodiment. Thus, due to a temperature increase onthe magnetic head 2 or heat generated on the head element itself, thethermal expansion films are expanded together with the head element,resulting in deformation around the head element part. Therefore, thehead element does not relatively protrude toward the magnetic disk,thereby avoiding direct collision between the head element and the smallprotrusion on the surface of the magnetic disk. Thus, it is possible toprevent damage on the head element and an abnormal signal caused by theformation of thermal asperity.

Referring to FIGS. 19 and 20, Embodiment 5 of the present invention willbe discussed by taking a magnetoresistance type head as an example. InFIG. 19, since the configuration of a magnetic head 2 is identical tothat of Embodiment 1, the explanation thereof is omitted. At the side ofthe slider from a head element part 3, a thermal expansion film 17 c isformed on the side of a disk 10 from a central surface of a thickness ofthe slider or the magnetic head substantially in parallel at apredetermined interval from the head element part 3.

Next, referring to FIG. 20, the operation of the present embodiment willbe discussed. In the case of the present embodiment, even when the headelement is subjected to thermal expansion due to a temperature increaseon the magnetic head and the head element protrudes to the magneticdisk, the thermal expansion film 17 c formed adjacent to the slider isalso subjected to thermal expansion, and the rear of the thermalexpansion film is bent in a direction of moving away from the disk 10.Thus, it is possible to maintain a spacing between the head element part3 and the protrusion 11 on the disk 10, thereby avoiding collisionbetween the head element and the small protrusion. For this reason, itis possible to prevent an abnormal signal resulted from damage on theelements and the formation of thermal asperity.

By selecting a material of the thermal expansion film 17 and adjustingthe size and the forming position of the thermal expansion film 17, adeformation amount of the magnetic head 2 due to heat can be adjusted asnecessary. As an example, the following case will be discussed: anelement material is a Ni—Fe alloy with a linear thermal expansioncoefficient δl/l of 1.45×10⁻⁵/K, the head element is 0.05 mm in lengthin a thickness direction of the slider, and an insulation film is madeof alumina with a linear thermal expansion coefficient δl/l of7.5×10⁻⁶/K. When a temperature is increased by is 20K, it was determinedby calculation that the element has a protrusion amount δl of 7 nm.Thus, in order to make deformation equal to a protrusion amount of theelement, a pico slider with a slider thickness of 0.3 mm is preferablyadopted. Besides, when a thermal expansion film whose thermal expansioncoefficient δl/l is 2.9×10⁻⁵/K is adopted, the thermal expansion filmmay be set at 0.05 mm in thickness and a distance may be set at 0.15 mmbetween the thermal expansion film and the element.

Next, referring to FIG. 22, a magnetic head slider according to anotherembodiment of the present invention will be discussed. Since theconfiguration of a head element part 3 is identical to that of abovedescribed Embodiment 1, the explanation thereof is omitted. Close to theside of a slider 1 from a head element part 3, a thermal expansion film9 is formed at a predetermined interval from the head element part 3substantially in parallel in the magnetic disk surface direction of theslider on the side of the disk 12 from a central line of a thickness ofthe slider. Further, electric conduction lines 14 a and 14 b or electricconductive films are provided for applying voltage to the thermalexpansion film 9. A temperature of the thermal expansion film can becontrolled by applying voltage.

In the present embodiment, the thermal expansion film is disposed insidea magnetic head film member 2 where the magnetic head element 3 isformed, and the thermal expansion film is disposed near the element.Furthermore, the thermal expansion film 9 is disposed along a jointsurface of the magnetic head film member 2 and the slider body 1.

The operation of the present embodiment will be discussed below.Regarding the effect of preventing damage on the head element andthermal asperity by thermal expansion of the thermal expansion film 9,the present embodiment is identical to the above described examples, sothat the explanation thereof is omitted. However, by adjusting voltageapplied to the thermal expansion film 9, expansion of the thermalexpansion film can be adjusted to a quantity suitable for preventingdamage on the element. For example, a controlling method similar to thatof Embodiment 5 may be adopted.

Moreover, the thermal expansion film 9 is provided along the jointsurface of the magnetic head (film) 2 and the slider body 1, and themagnetic head element part 3 is disposed on the side of the rear end(the side of an air flow-out end) of the slider of the expansion film 9.Additionally, since the thermal expansion film 9 is disposed near themagnetic disk in a thickness direction of the slider, it is possible toreadily adjust a protrusion amount of the head element 3 and to largelydeform the magnetic head film member 2 with ease in a direction ofmoving away from the disk 12.

As is apparent from the above description, according to the abovedescribed embodiment of the present invention, even when an ambienttemperature rises, or even when a temperature of the element isincreased by writing and reading, it is possible to maintain a fixed andproper temperature of the element by changing voltage or current appliedto the electric conducting films. By maintaining a proper and fixedspacing between the element and the writing medium, it is possible toprevent damage on the head element and an abnormal signal resulted fromthe formation of thermal asperity without causing the head element tocollide with the small protrusions on the surface of the magnetic disk.

Further, when the element has a low temperature, voltage or current isapplied to the electric conducting films and heat is generated on theelectric conducting films so as to maintain a fixed and propertemperature of the element. Thus, a proper and fixed spacing ismaintained between the element and the writing medium so as to prevent awriting/reading error at low temperature.

As described above, according to the present invention, it is possibleto provide a magnetic disk device or a magnetic head slider, by whichcollision can be prevented between the head element and the smallprotrusions on the surface of the magnetic disk even when a temperatureincreases, and damage on the head element and thermal asperity can bereduced.

Moreover, it is possible to provide a magnetic disk device which canperform normal writing and reading in response to changes in ambienttemperature such as a temperature in the magnetic disk device and anoutside air temperature.

1. A magnetic head slider comprising: a slider to float on an air streamof a rotating magnetic disk; an insulating film formed on the slider, amagnetic head element which is formed on the insulating film to recordinformation on the magnetic disk or to reproduce information from themagnetic disk; and a film heat source formed between the magnetic headelement and the slider; wherein the insulating film is formed betweenthe film heat source and the slider, and is formed on a side facing tothe magnetic disk with respect to the film heat source so as to cover anend of the film heat source.
 2. A magnetic head slider according toclaim 1, wherein the film heat source is formed with an electricconducting film, and the insulating film is heated by conductingelectricity to the electric conducting film.
 3. A magnetic head slideraccording to claim 2, wherein a distance between the magnetic headelement and the magnetic disk is adjusted by controlling the deformationof the insulating film by adjusting temperature change by controllingcurrent flow to the electric conducting film.
 4. The magnetic headslider according to claim 3, wherein distance adjustment is made usingthe deformation to selectably move the magnetic head element in adirection defined by close to or away from a surface of the magneticdisk.
 5. The magnetic head slider according to claim 1 or 2,characterized in that the film heat source is disposed near the magneticdisk surface side of the slider.
 6. magnetic disk device comprising: arotatable magnetic disk; a slider supported and separated by a gap fromthe magnetic disk, wherein the slider includes an insulating film formedthereon; a magnetic head element which is formed on the insulating filmto record information on the magnetic disk or to reproduce informationfrom the magnetic disk; a film heat source formed between the magnetichead element and the slider; where the insulating film is formed betweenthe film heat source and the slider, and is formed on a side facing tothe magnetic disk with respect to the film heat source so as to cover anend of the film heat source; a suspension for supporting the slider; acarriage for movably supporting the suspension relative to the magneticdisk; and means for adjusting heat generation of the heat source.
 7. Amagnetic disk device comprising: a rotatable magnetic disk; a slidersupported and separated by a gap from the magnetic disk, wherein theslider includes an insulating film formed thereon; a magnetic headelement which is formed on the insulating film to record information onthe magnetic disk or to reproduce information from the magnetic disk; aheat source formed between the magnetic head element and the slider,where the insulating film is formed between the heat source and theslider, and is formed on a side facing to the magnetic disk with respectto the heat source so as to cover an end of the heat source; asuspension for supporting the slider; a carriage for movably supportingthe suspension relative to the magnetic disk; and adjusting means foradjusting heat generation of the heat source.
 8. The magnetic diskdevice according to claim 7, comprising: means for loading or unloadingthe slider and the suspension with respect to the magnetic disk, andwherein the adjusting means performs heating of the heat source when thesuspension is loaded on the magnetic disk.
 9. The magnetic disk deviceaccording to claim 7 comprising: means for loading or unloading theslider and the suspension with respect to the magnetic disk, and whereinthe adjusting means reduces heat from the heat source when thesuspension is unloaded from the magnetic disk.
 10. The magnetic diskdevice according to any of claims 6 to 9, wherein the heat source isdisposed adjacent to a magnetic disk surface side of the slider.
 11. Themagnetic disk device according to any of claims 6 to 9, wherein a tipend of the magnetic head element at a surface side opposing to themagnetic disk is made concave toward a back surface side of the slidermore than a surface opposing to the magnetic disk of the slider.